Glycera dibranchiata is exactly the kind of creature you don’t want to find at the bottom of your beach bucket. They are called bloodworms for their translucent skin. Long and venomous, the worms are native to both coasts of North America and have four sharp fangs and a somewhat grumpy temperament: As they burrow through the sand, they will attack whatever they sense nearby.
“They get very protective of their turf,” said Herbert Waite, a professor at the University of California, Santa Barbara, who studies the creatures. “I think they’re basically introverts.”
When disgruntled, the worms shoot out a proboscis of peculiar construction to grip their prey.
“You can imagine if your head was a balloon, normally it’s sucked inside your body. Then, when you want to eat, you inflate it and bite and then suck it back in, ”said William Wonderly, a chemist also at Santa Barbara who collaborated with Dr. Waite to study the creatures. “It reminds me a lot of the aliens in ‘Alien,’ where they have a little mouth that they shoot out and retract.”
The worms have another feature that is less obvious but just as odd. Their fangs, which sprout from specialized cells on their skin, are devilishly hard and made up of just three ingredients, including melanin. While melanin is one of the pigments behind human skin and hair color, bloodworms somehow make it into a tough material infused with copper, which makes up a whopping 10 percent or so of the fangs by weight. But how the worms pull off the chemical transformation used to be a mystery.
In a paper published Monday in the journal Matter, Dr. Wonderly, Dr. Waite and colleagues revealed that the creatures do it by relying on the third ingredient in the fangs, a deceptively simple protein with many talents. The finding unlocks a biochemical secret of this unusual creature and highlights how nature finds surprisingly simple ways to build complex anatomical features.
A bloodworm’s fangs grow out of a set of cells that function as hoppers, storing the materials for their assembly, Dr. Wonderly said. The team examined the proteins being used in these cells and pinpointed one, called a multitasking protein, as a major component of the final product. This protein, they report in the new paper, is made mainly of just two amino acids, a small number, but it plays a crucial role in the fang’s assembly.
The scientists found that the protein catalyzes a reaction to create melanin and recruits copper ions. Then, it links melanin into polymers, assembles itself and melanin into a structure and uses the copper to seal the whole thing together. Essentially, the multitasking protein seems to steer melanin away from its tendency to form into the blobs you’d see microscopically in human hair and skin, Dr. Wonderly said. That allows it to become something totally different: part of a lethal killing machine that hides in sand.
Not all of the bloodworm’s mysteries are solved: Little is understood about how the organism first evolved this system and how copper is handled within the worm’s body.
“A huge question is how the copper gets concentrated in the jaws,” Dr. Wonderly said. “To really understand, you would need the baby worms. But because they have a complicated spawning cycle, they’re hard to grow in the lab. ”
The team is hoping to learn more about how the worms assemble this unusual polymer by tracing how the melanin is produced and how the worm builds it from precursors within its body.
“There are so many things that nature has figured out how to do in a very efficient, clever way,” Dr. Waite said. “It requires basic science and a childlike curiosity to uncover.”